1. Field of the Invention
The present invention relates to a thermal processing apparatus and, more specifically, to a thermal processing apparatus for performing heat processing for a substrate, for example, a semiconductor wafer, an LCD glass substrate or the like.
2. Description of the Related Art
Generally, in manufacture of a semiconductor device, the photolithography technology is used to form a thin film of ITO (Indium Tin Oxide) and an electrode pattern on a semiconductor wafer, LCD glass substrate, or the like (hereinafter, referred to as a substrate). In the photolithography technology, a photoresist is applied on the wafer, a resist film formed by the application is exposed to light according to a predetermined circuit pattern, and the exposed pattern is subjected to developing treatment to form a circuit pattern in the resist film.
In the photolithography process, various kinds of heat processing are performed, such as heat processing after the resist application (pre-baking), heat processing after exposure (post exposure-baking), heat processing after developing treatment (post-baking) and so on.
In those kinds of heat processing in the prior art, for example, in the pre-baking, a purge gas, for example, air, a nitrogen gas (N2) or the like is supplied into a processing chamber housing a wafer or the like, and the gas used for the processing is exhausted to the outside via an exhaust pipe connected to the processing chamber. In this event, a small amount of sublimate, for example, an acid generating material contained in the photoresist, such as PAG (Photo Acid Grain) or a foreign substance such as a low molecular resin constituting the resist is generated during the heating from the resist film formed on the front surface of the wafer or the like. In particular, the sublimate is often generated from the photoresist using a nonionic acid generating material with a low boiling point.
Accordingly, in the prior art, an impurity collecting portion for the sublimate and the like is provided along an exhaust line such as the exhaust pipe or the like, and a plurality of current plates for exhaust are provided on the peripheral side portion of the lid body constituting the processing chamber in order to evenly disperse the exhaust in conjunction with the impurity collecting portion (Claims and FIG. 4 of Japanese Patent Application Laid-open No. 2003-318091).